Pet as edge seal for multilaminated compositions

ABSTRACT

This invention provides an edge seal that employs Polyethylene Terephthalate (PET) adhered to the edge of a laminated glass by a layer adhesive material in order to improve the protection against environmental conditions. The edge seal claimed by this invention also acts as a scratch resistant material, helping to prevent edge marring during handling, transport and installation of the laminated glass product. This edge can be applied to architectural or transportation laminated glass constructions, either flat or curved, including bullet resistance glass.

FIELD OF THE INVENTION

This invention is related to automotive and architectural LaminatedGlass (LG), which includes Bullet Resistant Glass (BRG). Specifically,it relates to edge seals for laminated glass.

A laminated glass construction is composed by several layers of glassjoined with different polymers (e.g. polyvinyl butyral, polyurethane)and usually a layer of polycarbonate (in the case of BRG), with thepurpose of absorbing energy to avoid penetration of foreign objects.FIG. 1 shows a scheme of a typical BRG laminated glass construction.

Making reference to FIG. 1, a typical illustrative BRG laminated glassconstruction can be formed by a plurality of laminated glass sheets (1)sandwiched between films of polyvinyl butyral (PVB) (2) (wherepolyurethane can also be used), and an inner layer of polycarbonate (3)joined to the glass sheets by a layer of polyurethane (5). There is alsoa final hard coat layer (4) used to prevent the splinter glassprojection under ballistic attacks, which is joined to the polycarbonatewith another layer of polyurethane. Other polymers can also be used inthese layers, such as acrylic, EVA, polyester, polyethylene ionomer,Surlyn® (Sentry Glass Plus), acrylic resin and any ionomericmodification of these polymers. These layers can be of uniform thicknessor may have different thickness according with the protection level ofthe laminated construction. In addition, the glass and polymer layerscan be located in any order within the construction, without necessarilyfollowing the strict order illustrated in FIG. 1. A typical laminatingprocess consist of introducing the plies comprising the laminated glassconstruction into an autoclave, where the construction is subjected topressure and temperature conditions for a time required to laminate allthe materials.

As used herein, the following terms are understood to mean:

Glass: Refers to any translucid, vitreous-ceramic or ceramic material(e.g. soda-lime, boro-silicate, alumino-silicate, silica); that may beused as layer in a laminated glass construction;

Laminated Glass: a construction composed by one or more glass layersbonded together with one or more films of polymeric material;

Bullet Resistant Glass (BRG): a laminated glass construction thataffords a defined resistance against the firing of specified weapons andammunitions, according to international standards such as EuropeanCommittee for Standardization (CEN-EN1063), Underwriters Laboratory(UL-752), and National Institute of Justice (NIJ-0108.01);

TPU (PU-E): Polyurethane thermoelastomer Film.

PET: Polyethylene Terephthalate;

Edge: All planar, rounded or beveled surfaces that run along theperimeter of some or all the layers composing a Laminated Glass;

Edge Seal: Construction composed by one or more layers of materials thatis used for covering the edge in a laminated Glass.

Laminated glass preferably requires boundary protection along its edgein order to prevent or at least prolong water vapor and solventmigration to the interfaces between the different layers making up thelaminated glass. FIG. 2 a illustrates an edge seal (5) along a laminatedglass structure with an offset layer (20) that is nor covered by theedge seal. FIG. 2 b illustrates another laminated glass structure(without an offset layer) with an edge seal (5) that covers all of thelayers. Once water vapor penetrates the laminated glass structure itwill eventually reach the interface with the polymer film, typicallyPVB. As shown in FIG. 4, since PVB has a hygroscopic molecularstructure, the PVB film absorbs the molecules of S water into itspolymeric matrix, which eventually migrate to the interface between theglass and PVB and create a breaking or repulsion effect between theadhesion bonds of the PVB and the glass. When the adhesion bonds breakdown the layers start to delaminate, creating an unsightly bubble withinthe laminated glass and eventually

compromising the integrity of the entire structure.

In order to try and solve the foregoing problem, commercially availablelaminated glass is typically protected along its edge with a film ofpolyurethane (TPU). This edge seal also provides shock-absorbingprotection to prevent edge cracks in the laminated glass. However, TPUhas important shortcomings that prevent it from providing an effectivesolution to the problems it pretends to solve. For one, TPU has watervapor permeability

of 25 g/cm2.day.bar, allowing water vapor migration to affect theintegrity of the laminated glass in unacceptably short periods around(i.e. less than 24 months). Additionally, TPU has another importantcomplication that arises from the application of primers and adhesivesused to install the laminated glass. These adhesive compounds (e.g.aromatics such as methyl di-isocyanate (MDI), toluene di-isocyanate(TDI), aromatics di-isocyanates, etc.) chemically attack the structureof TPU, specifically breaking down the molecular structure and inducingincreased permeability that permits the migration of the aromaticisocyanates to the interior of the laminated glass. Temperaturefluctuations also make the TPU film expand and contract, which alsofavors the diffusion of aromatic isocyanates compounds into thelaminated glass. The water vapor present in the laminated glass thencatalyzes a cross-link reaction between the aromatic isocyanates and theTPU of the laminated glass (see FIG. 5), all of which results in thegeneration of a commercially unacceptable yellowish hue in the laminatedglass and the loss of adherence between the TPU and the glass layers.

The prior art discloses attempts at solving the foregoing problems. EP0391 165 A3 describes the sealing of the edge of an automotive glasslaminate by means of a synthetic resin of the fluoropolymer, polybutenepolymer or butylpolymer type applied to a planar or simple perimetraledge of the glass laminate. U.S. Pat. No. 5,908,675 teaches an edge sealcomprised by a flowable ethylene-polymer-in-water emulsion to form astructure layer of the emulsion following a the macrogeometry of theedge specify the adhesive material. U.S. Pat. No. 6,649,695 teaches, atan edge sealed, the use of block copolymers that contain at least onepolymer block which is composed of isobutene units and at least twofurther polymer blocks that are composed of units derived fromvinylaromatic monomers. CN1344857 uses a neutral sealing silicone glueas an edge seal, which is compatible with PVB and waterproof. DE19824965discloses a hot-melt adhesive as an edge seal that has been producedaccording to cast-resin technology. The inventive adhesive comprisesacrylate or metacrylate homopolymers or copolymers or mixtures thereof.The invention also relates to a method for the production and to theuses of said hot-melt adhesive.

SUMMARY OF THE INVENTION

In its preferred embodiment, this invention provides an edge seal thatemploys Polyethylene Terephthalate (PET) adhered to the edge of alaminated glass by a layer of TPU in order to improve the protectionagainst the water vapor and solvent migration into the laminated glassconstruction. Moreover the PET in the edge imparts an attractive surfacefor the edge of the finished laminated glass product. This feature ishighly appreciated by consumers in the laminated glass market. The edgeseal claimed by this invention also acts as a scratch resistantmaterial, helping to prevent edge marring during handling, transport andinstallation of the laminated glass product.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be further described with reference being made tothe accompanying drawings, none of which are to scale and all of whichare schematic in nature.

FIG. 1. Cross-sectional side view of an illustrative commerciallyavailable BRG laminated glass product with no edge seal.

FIG. 2 a. Cross-sectional side view of a commercially available EdgeSeal used in an offset laminated glass construction.

FIG. 2 b. Cross-sectional side view of a commercially available EdgeSeal used in a non-offset laminated glass construction.

FIG. 3. Schematic view of the bagging process required for thisinvention.

FIG. 4. Schematic view illustrating the detrimental effect of watermolecules on the adhesion phenomena at the interface between the glassand PVB layers in laminated glass.

FIG. 5. Schematic view of the chemical reaction among TPU, water vaporand aromatic isocyanates.

FIG. 6. Schematic view preferred embodiment 1.

DETAILED DESCRIPTION OF THE INVENTION

The literature shows there are different polymeric materials which havelow permeability and high chemical resistance properties that couldpotentially present a solution to the problems exposed above, such as:Polyethylene High Density (PE-HD). Polyacetal (POM). Polyethylene LowDensity (PE-LD). Polyamide 12 (PA 12). Polypropylene (PP).Polyethyleneterepthalate (PET). PolyVinylChloride Rigid (PVC-U).

In the Table 1 and 2 are shown the permeabilities and the chemicalresistance of these materials. Polyurethane Elastomers (PU-E) isincluded for comparative purposes. TABLE 1 Film O₂ Temp. Thickness WaterVapor (cm³/m² Polymer ° C. (μm) (g/cm² day) day bar) PE-LD 23 100 1 2000PE-HD 25 40 0.9 1890 PP 25 40 2.1 1900 PVC-U 20 40 7.6 87 POM 20 40 2.550 PA 12 25 25 0.35 800 PET 23 25 8 110 PU-E 23 25 13 1000

TABLE 2 Strong Weak Hot Weak Strong Alkali Alkali Aromatic KetonesOrganic Polymer Water Acids Acids Sln Sln Hydrocarb. Esters Ethers AcidsPE-LD + + • + + − • •/− + PE-HD + + + + + • + +/• + PP + + • + + • • •/−• PVC-R + + + + + − − − − POM + • − + + • − •/+ + PA 12 + − − + • + ++/+ • PET + + • • − + + +/+ + PU + • − • • − + −/− − Elastomers+ Resistant• Limited Resistance− Not Resistant

In order to study adherence behavior with TPU and laminated glass,adherence tests using the polymers mentioned above were performed,obtaining the results found in Table 3. These materials were laminatedin an autoclave process holding a 120-200 psi pressure at 95-140° C.temperature pursuant to ASTM D3167. TABLE 3 Adherence AdherenceAdherence to to TPU to Glass Polycabonate(PC) ASTM 3167 ASTM 3167 ASTM3167 Polymer Ciclo (N/mm) (N/mm) (N/mm) PE-LD 1 0.5 0.5 0.1 PE-HD 1 0.00.0 0.0 PP 1 0.1 0.1 0.0 PVC-U 1 0.3 0.3 0.2 POM 1 0.0 0.0 0.2 PA 12 11.0 0.1 0.5 PET 1 2.3 0.2 0.1 PU-E 1 25 0.0 23

From this table one can conclude that the first 5 polymers do notprovide good adherence performance when laminated under the givenlaminating variables. In the same way, one can observe that the lastthree polymers offer an acceptable adhesion performance.

Chemical resistance test of the mentioned polymers were also perfomedusing commercial adhesive compounds and other chemical substances foundin primers, the results being tabulated in Table 4. TABLE 4 Methyl PUSulfuric NaOH NaOH Ethyl Acetic Sika PU Acids 95% 40% Xilene/ EthylKetone Acid Polymer 256 U-438 (98%) Sln Sln Toluene Acetate (95%) (75%)PE-LD + + • + + • • • + PE-HD + + + • + • + • + PP + + • + + • • • •PVC-R + + • + + − − − − POM + • − + + • − • + PA 12 + − − + • + + + •PET + + + • • + + + + PU • − • • • − + • − Elastomers+ Resistant• Limited Resistance− Not Resistant

From this table one can observe that PET film has the highest chemicalresistance as well. This test also confirms the limited resistance ofthe PU elastomer used in the prior art.

The crucial test, which clearly suggested that PET was the best optionto be used as an edge seal, was the accelerated aging AGP-TLCC07 test(available from American Glass Products upon request, www.agpglass.com). This type or test is widely used to simulate extreme environmentalconditions on a laminated glass construction. The conditions of thistest are: each cycle has a total duration of 240 hours; temperatureranging from −30 to +85° C.; relative humidity ranging from 0-50%; UVradiation intensity equal to 125 W/m² for the range of wave lengthbetween 220 to 630 nm, which generates 70.2 MJ/m² energy for the totalcycle is duration. Two AGP-TLCC07 cycles are approximately equal to 1year in-use period. At the end of each cycle, the laminated glass issearched for de-lamination defects, air bubbles, tears and fracturesbetween any two bonded layers. The results are shown in Table 5, anddemonstrate that PET as an edge seal was the one option that satisfiednot only the processing requirements of laminated glass, but also thedurability ones. TABLE 5 Test Aging. POLYMER CYCLE CYCLE CYCLE CYCLECYCLE CYCLE CYCLE CYCLE CYCLE CYCLE FILM 1 2 3 4 5 6 7 8 9 10 PU-E W W WW F F F F F F W W W W W W F F F F W W W W W W F F F F W W W W W W W W FF W W W W W W W W W F PET W W W W W W W W F F W W W W W W W W F F W W WW W W W W W F W W W W W W W W W W W W W W W W W W W W PA 12 W W W F F FF F F F W W W W W F F F F F W W W W W W W F F F W W W W W W W F F F W WW W W W W W F F Control W W F F F F F F F F No edge W W W W F F F F F Fseal W W W W F F F F F F W W W W W F F F F F W W W W W W F F F FW = Perfect ConditionsF = Failure

This invention relates to an edge seal made with a PolyethyleneTerephthalate (PET) film, preferably treated with a hard coating ofpolysiloxane chemical family for improving the abrasion resistance. ThisPET film is adhered to the edge of the laminated glass by means of anadhesive sheet that may be made of a polyurethane thermo-elastomeric(TPU) material, butyral, acrylic or ethyl vinylic. In the most preferredembodiment illustrated in FIG. 6, an edge seal (21) is manufactured bycombining a 0.18 mm thick PET layer (6) with a 0.62 mm Polyurethaneadhesive sheet (PE399 Huntsman) (5). The PET layer is produced bystripping the PVB layer from the Spallshield® product sold by E.I.DuPont de Nemours (Wilmington, Del.), which is a combination PET/PVBfilm. This PET film also has a hard coating along its external surface(the one opposite the polyurethane sheet) provided by a polisiloxanetreatment. Alternatively the PET film may be left untreated in order tooptionally allow one or more additional layers of other materials to beadded, for example black urethane.

The method for making this invention may be summarized as follows. Thetypical assembly process of laminated glass is well known amongst thoseversed in the art. In essence, it involves arranging (sandwiching) theglass (curve or flat shapes) and polymeric plies in an appropriatefashion in order to produce the finished laminated glass product. Oncethe plies are arranged, a polyurethane film is placed around the edge ofthe laminated assembly. Next, the PET film is applied over thepolyurethane film. Once this assembly is fixed, the traditional pressureand temperature treatment can be applied in order to laminate the entireassembly and obtain the finished product. In order to guarantee theoutlet of air from the laminated assembly (de-aeration is necessary inorder to avoid leaving entrapped vapors or solvents), and since thepresence of the PET film prevents these trapped substances from laterbeing expelled (it was found that PET's lack of permeability is ahindrance in this regard), it was necessary to use a breathing film (8)along the exposed Polyurethane/PET interphase, preferably made fromnylon (Bleeder Lease® B Airtech Co.). Additionally, to achieve gooddimensional stability of the edge seal, a mold (14) with a triangularcross section made from silicone rubber with a hardness of 60-80 Shore Awas applied along the edge seal. FIG. 3 illustrates this assembly. Thisassembly is provisionally fixed with tape, placed in a bag (9) connectedto a vacuum system (10), vacuum is applied to a level of 20-21.5 in Hg.This vacuum level is held during all the laminating process, which isperformed in an autoclave, maintaining 100-200 psi pressure and 95-140°C. temperature during approximately 6-12 hours. The exact value of thesevariables depends on the laminated glass product.

The use of PET as an edge protection for curve and flat Bullet ResistantGlass presented certain problems that had to be overcome. The mainproblems were the presence of air bubbles, wrinkles and partial loss ofadhesion. Solutions to these problems obligated the inclusion of somemodifications to the conventional manufacturing process of laminatedglass products.

Air Bubbles: The formation of bubbles on any interface of the laminatedglass indicates a direct loss of adhesion and the consequent decrease ofballistic properties and reduced life of the laminated glass product.The solution to this problem involves the use of the breathing filmmentioned above and increasing the laminating pressure.

Wrinkles: PET is a material much more rigid than Polyurethane. Thus, ithas been found that for curved laminated glass pieces, PET presents somedifficulties to adapt to the composite curve (curve in 3-directions) oncorners of automotive laminated glass pieces. It is widely known thatlaminated glass constructions require during the autoclave process acover plate to laminate the upper polymeric ply (hard coated layer). Thecover plate, which most of cases is a glass ply, is discarded after theautoclave process. To control the presence of these wrinkles, we havefound an effective solution by cutting the cover plate 1.5 mm largerthan the size of the laminated glass piece, just on the corners. The 1.5mm space is then filled naturally by the melted Polyurethane used forbonding the upper polymeric ply to the laminated glass constructionwhich is also cut 1.5 mm larger.

Partial Loss of Adhesion: It was found in some cases that the PET usedas edge protection on curved and flat laminated glass constructionspresented partial loss of adhesion manifested in point specificdelaminations (5×5 mm sections). It was generally found that byincreasing the holding laminating temperature by 4° C. was enough toovercome the problem.

1. An edge seal for laminated glass that includes a PET layer adhered tothe edge of said laminated glass by means of one or more adhesivematerials, wherein the PET layer is at least partially covered with ascratch resistant coating along its external surface.
 2. The edge sealof claim 1, wherein the adhesive material is polyurethane.
 3. The edgeseal of claim 1, wherein the scratch resistant coating is comprised ofpolisiloxane material.
 4. The edge seal of claim 1, wherein thelaminated glass is bullet resistant glass.
 5. The edge seal of claim 1,wherein the laminated glass is to be used in transportationapplications.
 6. The edge seal of claim 1, wherein the laminated glassis curved.
 7. The edge seal of claim 1, wherein the scratch resistantcoating is covered by one or more layers of additional material.
 8. Anedge seal for a laminated glass that includes a polymer layer to theedge of said laminated glass by means of one or more adhesive materials,wherein said polymer layer: i) shares similar water vapor permeability,adherence and hardness characteristics as PET and; ii) is at leastpartially covered with a scratch resistant coating along its externalsurface.